Add support for dynamic channels in WebrtcTransport.

remoting/protocol/ice_connection_to_host.cc

Index: remoting/protocol/ice_connection_to_host.cc
diff --git a/remoting/protocol/ice_connection_to_host.cc b/remoting/protocol/ice_connection_to_host.cc
index 940ad856f30b191df9df9b822d6f4edd0d096b1f..503aedc4130137598ed7d0bb2ddc25c8375dc266 100644
--- a/remoting/protocol/ice_connection_to_host.cc
+++ b/remoting/protocol/ice_connection_to_host.cc
@@ -168,6 +168,12 @@ void IceConnectionToHost::OnChannelInitialized(
   NotifyIfChannelsReady();
 }
 
+void IceConnectionToHost::OnChannelClosed(
+    ChannelDispatcherBase* channel_dispatcher) {
+  // ICE transport doesn't close channels dynamically.
+  NOTREACHED();
+}
+
 void IceConnectionToHost::OnVideoChannelStatus(bool active) {
   event_callback_->OnConnectionReady(active);
 }